Add +fold flag to lang/latex for TeX-fold

modules/lang/latex/README.org

@@ -30,6 +30,8 @@ Provide a helping hand when working with LaTeX documents.
 ** Module Flags
 + =+latexmk= Use LatexMk instead of LaTeX to compile documents.
 + =+cdlatex= Enable [[https://github.com/cdominik/cdlatex][cdlatex]] for fast math insertion.
++ =+fold= Use TeX-fold (from auctex) to fold LaTeX macros to unicode, and make
+  folding hook-based and less manual.
 
 ** Plugins
 + [[http://www.gnu.org/software/auctex/][auctex]]